As a conventional display unit using coherent light, there has been known a display unit using a spatial modulation element as disclosed in Patent Document 1 (Japanese Published Patent Application No. 2003-98476 (Page 4, FIG. 1)). In addition to the display unit disclosed in Patent Document 1, there is a display unit which projects coherent light on a screen using a polygon mirror as shown in FIG. 7(a). Hereinafter, a conventional laser display unit shown in FIG. 7(a) will be described.
FIG. 7(a) is a diagram illustrating a schematic construction of the conventional laser display unit.
The laser display unit 100 includes laser light sources 101a˜101c corresponding to three colors of R, G, B, and optical modulator 106a˜106c for subjecting laser beams La˜Lc emitted from the laser sources 101a˜101c to intensity modulation according to primary color signals Sa˜Sc of an input video signal. Further, the laser display 100 includes a dichroic mirror 102a for wave coupling the laser beam Lb modulated by the optical modulator 106b and the laser beam Lc modulated by the optical modulator 106c, and a dichroic mirror 102b for wave coupling the laser beam La modulated by the optical modulator 106a and the laser beam from the dichroic mirror 102a. Further, this laser display 100 includes a polygon mirror 104 for scanning the laser beam wave coupled by the dichroic mirror 102b in an x direction, a galvanometer mirror 105 for scanning the light from the polygon mirror 104 in a y direction so that a two-dimensional image is formed on a screen 108, and a projection lens 107 for projecting the laser beam emitted by the galvanometer mirror on the screen 108.
Next, the operation will be described.
The laser beams La˜Lc from the laser sources 101a˜101c corresponding to the three colors of R, G, and B are subjected to intensity modulation by the optical modulators 106a˜106c according to the respective primary color signals Sa˜Sc of the input video signal, and then wave coupled by the optical system comprising the dichroic mirrors 102a and 102b. Further, the laser beam wave coupled by the dichroic mirror 102b is scanned in the x direction by the polygon mirror 104 and in the y direction by the galvanometer mirror 105. The laser beam scanned in the two-dimensional direction is projected on the screen 108 by the projection lens 107, whereby a two-dimensional image is displayed on the screen 108.
As described above, in the conventional laser display 100, since the light beams emitted from the laser sources 101a˜101c corresponding to R, G, B are monochromatic light beams, a displayable color range becomes wider than that of an NTSC signal by using laser sources of appropriate wavelengths, and further, a vivid image having high chromatic purity is possible.
FIG. 7(b) is a diagram illustrating devices connectable to the conventional laser display unit. The laser display unit 100 shown in FIG. 7(b) has R, G, B terminals to which a video signal is inputted, and any device can be connected to the laser display unit 100 so long as it has an output terminal of an RGB signal, such as a personal computer 201 like a notebook PC, a video game machine 202, an optical disc player 203 such as a DVD, an optical disc recorder 204 including a recorder with VTR, a VTR with a camera 205, a stationary VTR 206, a BS/CS tuner 207, a TV 208, a hard disk recorder 209 including recorders with various kinds of disk drives, an internet broadcasting STB (Set Top Box) 210, a CATV STB 211, a terrestrial digital broadcasting STB 212, or a BS HDTV STB 213.
Further, a D4 input terminal, a DVI-D input terminal, an IEEE1394 terminal, a component terminal, an S terminal, a video terminal and the like may be provided according to the formats of the signals outputted from the devices connected to the laser display.